Introduction

The AJP Connector element represents a
Connector component that communicates with a web
connector via the AJP protocol. This is used for cases
where you wish to invisibly integrate Tomcat into an existing (or new)
Apache installation, and you want Apache to handle the static content
contained in the web application, and/or utilize Apache's SSL
processing.

This connector supports load balancing when used in conjunction with
the jvmRoute attribute of the
Engine.

The native connectors supported with this Tomcat release are:

JK 1.2.x with any of the supported servers. See
the JK docs
for details.

mod_proxy on Apache httpd 2.x (included by default in Apache HTTP
Server 2.2), with AJP enabled: see
the
httpd docs for details.

Other native connectors supporting AJP may work, but are no longer
supported.

Attributes

Common Attributes

All implementations of Connector
support the following attributes:

Attribute

Description

ajpFlush

A boolean value which can be used to enable or disable sending
AJP flush messages to the fronting proxy whenever an explicit
flush happens. The default value is true.
An AJP flush message is a SEND_BODY_CHUNK packet with no body content.
Proxy implementations like mod_jk or mod_proxy_ajp will flush the
data buffered in the web server to the client when they receive
such a packet. Setting this to false can reduce
AJP packet traffic but might delay sending packets to the client.
At the end of the response, AJP does always flush to the client.

allowTrace

A boolean value which can be used to enable or disable the TRACE
HTTP method. If not specified, this attribute is set to false.

asyncTimeout

The default timeout for asynchronous requests in milliseconds. If not
specified, this attribute is set to the Servlet specification default of
30000 (30 seconds).

enableLookups

Set to true if you want calls to
request.getRemoteHost() to perform DNS lookups in
order to return the actual host name of the remote client. Set
to false to skip the DNS lookup and return the IP
address in String form instead (thereby improving performance).
By default, DNS lookups are disabled.

maxHeaderCount

The maximum number of headers in a request that are allowed by the
container. A request that contains more headers than the specified limit
will be rejected. A value of less than 0 means no limit.
If not specified, a default of 100 is used.

maxParameterCount

The maximum number of parameter and value pairs (GET plus POST) which
will be automatically parsed by the container. Parameter and value pairs
beyond this limit will be ignored. A value of less than 0 means no limit.
If not specified, a default of 10000 is used. Note that
FailedRequestFilterfilter can be
used to reject requests that hit the limit.

maxPostSize

The maximum size in bytes of the POST which will be handled by
the container FORM URL parameter parsing. The limit can be disabled by
setting this attribute to a value less than zero. If not specified, this
attribute is set to 2097152 (2 megabytes). Note that the
FailedRequestFilter
can be used to reject requests that exceed this limit.

maxSavePostSize

The maximum size in bytes of the POST which will be saved/buffered by
the container during FORM or CLIENT-CERT authentication. For both types
of authentication, the POST will be saved/buffered before the user is
authenticated. For CLIENT-CERT authentication, the POST is buffered for
the duration of the SSL handshake and the buffer emptied when the request
is processed. For FORM authentication the POST is saved whilst the user
is re-directed to the login form and is retained until the user
successfully authenticates or the session associated with the
authentication request expires. The limit can be disabled by setting this
attribute to -1. Setting the attribute to zero will disable the saving of
POST data during authentication. If not specified, this attribute is set
to 4096 (4 kilobytes).

parseBodyMethods

A comma-separated list of HTTP methods for which request
bodies will be parsed for request parameters identically
to POST. This is useful in RESTful applications that want to
support POST-style semantics for PUT requests.
Note that any setting other than POST causes Tomcat
to behave in a way that goes against the intent of the servlet
specification.
The HTTP method TRACE is specifically forbidden here in accordance
with the HTTP specification.
The default is POST

port

The TCP port number on which this Connector
will create a server socket and await incoming connections. Your
operating system will allow only one server application to listen
to a particular port number on a particular IP address. If the special
value of 0 (zero) is used, then Tomcat will select a free port at random
to use for this connector. This is typically only useful in embedded and
testing applications.

protocol

Sets the protocol to handle incoming traffic. To configure an AJP
connector this must be specified. If no value for protocol is provided,
an HTTP connector rather than an AJP connector
will be configured.
The standard protocol value for an AJP connector is AJP/1.3
which uses an auto-switching mechanism to select either a Java NIO based
connector or an APR/native based connector. If the
PATH (Windows) or LD_LIBRARY_PATH (on most unix
systems) environment variables contain the Tomcat native library, the
native/APR connector will be used. If the native library cannot be
found, the Java NIO based connector will be used.
To use an explicit protocol rather than rely on the auto-switching
mechanism described above, the following values may be used:org.apache.coyote.ajp.AjpProtocol
- blocking Java connectororg.apache.coyote.ajp.AjpNioProtocol
- non blocking Java NIO connector.org.apache.coyote.ajp.AjpNio2Protocol
- non blocking Java NIO2 connector.org.apache.coyote.ajp.AjpAprProtocol
- the APR/native connector.
Custom implementations may also be used.
Take a look at our Connector
Comparison chart.

proxyName

If this Connector is being used in a proxy
configuration, configure this attribute to specify the server name
to be returned for calls to request.getServerName().
See Proxy Support for more
information.

proxyPort

If this Connector is being used in a proxy
configuration, configure this attribute to specify the server port
to be returned for calls to request.getServerPort().
See Proxy Support for more
information.

redirectPort

If this Connector is supporting non-SSL
requests, and a request is received for which a matching
<security-constraint> requires SSL transport,
Catalina will automatically redirect the request to the port
number specified here.

scheme

Set this attribute to the name of the protocol you wish to have
returned by calls to request.getScheme(). For
example, you would set this attribute to "https"
for an SSL Connector. The default value is "http".

secure

Set this attribute to true if you wish to have
calls to request.isSecure() to return true
for requests received by this Connector. You would want this on an
SSL Connector or a non SSL connector that is receiving data from a
SSL accelerator, like a crypto card, a SSL appliance or even a webserver.
The default value is false.

URIEncoding

This specifies the character encoding used to decode the URI bytes,
after %xx decoding the URL. If not specified, UTF-8 will be used unless
the org.apache.catalina.STRICT_SERVLET_COMPLIANCEsystem property is set to true
in which case ISO-8859-1 will be used.

useBodyEncodingForURI

This specifies if the encoding specified in contentType should be used
for URI query parameters, instead of using the URIEncoding. This
setting is present for compatibility with Tomcat 4.1.x, where the
encoding specified in the contentType, or explicitly set using
Request.setCharacterEncoding method was also used for the parameters from
the URL. The default value is false.

Set this attribute to true to cause Tomcat to use
the IP address passed by the native web server to determine the Host
to send the request to. The default value is false.

xpoweredBy

Set this attribute to true to cause Tomcat to advertise
support for the Servlet specification using the header recommended in the
specification. The default value is false.

Standard Implementations

To use AJP, you must specify the protocol attribute (see above).

The standard AJP connectors (BIO, NIO, NIO2 and APR/native) all support
the following attributes in addition to the common Connector attributes
listed above.

Attribute

Description

acceptCount

The maximum queue length for incoming connection requests when
all possible request processing threads are in use. Any requests
received when the queue is full will be refused. The default
value is 100.

acceptorThreadCount

The number of threads to be used to accept connections. Increase this
value on a multi CPU machine, although you would never really need more
than 2. Also, with a lot of non keep alive connections, you
might want to increase this value as well. Default value is
1.

acceptorThreadPriority

The priority of the acceptor threads. The threads used to accept
new connections. The default value is 5 (the value of the
java.lang.Thread.NORM_PRIORITY constant). See the JavaDoc
for the java.lang.Thread class for more details on what
this priority means.

address

For servers with more than one IP address, this attribute
specifies which address will be used for listening on the specified
port. By default, this port will be used on all IP addresses
associated with the server. A value of 127.0.0.1
indicates that the Connector will only listen on the loopback
interface.

bindOnInit

Controls when the socket used by the connector is bound. By default it
is bound when the connector is initiated and unbound when the connector is
destroyed. If set to false, the socket will be bound when the
connector is started and unbound when it is stopped.

clientCertProvider

When client certificate information is presented in a form other than
instances of java.security.cert.X509Certificate it needs to
be converted before it can be used and this property controls which JSSE
provider is used to perform the conversion. For example it is used with
the AJP connectors, the HTTP APR connector and
with the
org.apache.catalina.valves.SSLValve.If not specified, the default
provider will be used.

connectionLinger

The number of seconds during which the sockets used by this
Connector will linger when they are closed. The default
value is -1 which disables socket linger.

connectionTimeout

The number of milliseconds this Connector will wait,
after accepting a connection, for the request URI line to be
presented. The default value for AJP protocol connectors
is -1 (i.e. infinite).

executor

A reference to the name in an Executor
element. If this attribute is set, and the named executor exists, the
connector will use the executor, and all the other thread attributes will
be ignored. Note that if a shared executor is not specified for a
connector then the connector will use a private, internal executor to
provide the thread pool.

executorTerminationTimeoutMillis

The time that the private internal executor will wait for request
processing threads to terminate before continuing with the process of
stopping the connector. If not set, the default is 0 (zero)
for the BIO connector and 5000 (5 seconds) for the NIO, NIO2
and APR/native connectors.

keepAliveTimeout

The number of milliseconds this Connector will wait for
another AJP request before closing the connection.
The default value is to use the value that has been set for the
connectionTimeout attribute.

maxConnections

The maximum number of connections that the server will accept and
process at any given time. When this number has been reached, the server
will accept, but not process, one further connection. This additional
connection be blocked until the number of connections being processed
falls below maxConnections at which point the server will
start accepting and processing new connections again. Note that once the
limit has been reached, the operating system may still accept connections
based on the acceptCount setting. The default value varies by
connector type. For BIO the default is the value of
maxThreads unless an Executor
is used in which case the default will be the value of maxThreads from the
executor. For NIO and NIO2 the default is 10000.
For APR/native, the default is 8192.

Note that for APR/native on Windows, the configured value will be
reduced to the highest multiple of 1024 that is less than or equal to
maxConnections. This is done for performance reasons.
If set to a value of -1, the maxConnections feature is disabled
and connections are not counted.

maxThreads

The maximum number of request processing threads to be created
by this Connector, which therefore determines the
maximum number of simultaneous requests that can be handled. If
not specified, this attribute is set to 200. If an executor is associated
with this connector, this attribute is ignored as the connector will
execute tasks using the executor rather than an internal thread pool.

minSpareThreads

The minimum number of threads always kept running. If not specified,
the default of 10 is used.

packetSize

This attribute sets the maximum AJP packet size in Bytes. The maximum
value is 65536. It should be the same as the max_packet_size
directive configured for mod_jk. Normally it is not necessary to change
the maximum packet size. Problems with the default value have been
reported when sending certificates or certificate chains. The default
value is 8192. If set to less than 8192 then the setting will ignored and
the default value of 8192 used.

processorCache

The protocol handler caches Processor objects to speed up performance.
This setting dictates how many of these objects get cached.
-1 means unlimited, default is 200. If not using
Servlet 3.0 asynchronous processing, a good default is to use the same as
the maxThreads setting. If using Servlet 3.0 asynchronous processing, a
good default is to use the larger of maxThreads and the maximum number of
expected concurrent requests (synchronous and asynchronous).

requiredSecret

Only requests from workers with this secret keyword will be accepted.

tcpNoDelay

If set to true, the TCP_NO_DELAY option will be
set on the server socket, which improves performance under most
circumstances. This is set to true by default.

threadPriority

The priority of the request processing threads within the JVM.
The default value is 5 (the value of the
java.lang.Thread.NORM_PRIORITY constant). See the JavaDoc
for the java.lang.Thread class for more details on what
this priority means.

tomcatAuthentication

If set to true, the authentication will be done in Tomcat.
Otherwise, the authenticated principal will be propagated from the native
webserver and used for authorization in Tomcat. Note that this principal
will have no roles associated with it.
The default value is true. If
tomcatAuthorization is set to true this
attribute has no effect.

tomcatAuthorization

If set to true, the authenticated principal will be
propagated from the native webserver and considered already authenticated
in Tomcat. If the web application has one or more security constraints,
authorization will then be performed by Tomcat and roles assigned to the
authenticated principal. If the appropriate Tomcat Realm for the request
does not recognise the provided user name, a Principal will be still be
created but it will have no roles. The default value is
false.

Java TCP socket attributes

The BIO, NIO and NIO2 implementation support the following Java TCP socket
attributes in addition to the common Connector and HTTP attributes listed
above.

(bool)Boolean value for the socket's keep alive setting
(SO_KEEPALIVE). JVM default used if not set.

socket.ooBInline

(bool)Boolean value for the socket OOBINLINE setting. JVM default
used if not set.

socket.soReuseAddress

(bool)Boolean value for the sockets reuse address option
(SO_REUSEADDR). JVM default used if not set.

socket.soLingerOn

(bool)Boolean value for the sockets so linger option (SO_LINGER).
A value for the standard attribute connectionLinger
that is >=0 is equivalent to setting this to true.
A value for the standard attribute connectionLinger
that is <0 is equivalent to setting this to false.
Both this attribute and soLingerTime must be set else the
JVM defaults will be used for both.

socket.soLingerTime

(int)Value in seconds for the sockets so linger option (SO_LINGER).
This is equivalent to standard attribute
connectionLinger.
Both this attribute and soLingerOn must be set else the
JVM defaults will be used for both.

socket.soTimeout

This is equivalent to standard attribute
connectionTimeout.

socket.performanceConnectionTime

(int)The first value for the performance settings. See
Socket Performance Options
All three performance attributes must be set else the JVM defaults will
be used for all three.

socket.performanceLatency

(int)The second value for the performance settings. See
Socket Performance Options
All three performance attributes must be set else the JVM defaults will
be used for all three.

socket.performanceBandwidth

(int)The third value for the performance settings. See
Socket Performance Options
All three performance attributes must be set else the JVM defaults will
be used for all three.

socket.unlockTimeout

(int) The timeout for a socket unlock. When a connector is stopped, it will try to release the acceptor thread by opening a connector to itself.
The default value is 250 and the value is in milliseconds

NIO specific configuration

The following attributes are specific to the NIO connector.

Attribute

Description

socket.directBuffer

(bool)Boolean value, whether to use direct ByteBuffers or java mapped
ByteBuffers. Default is false.
When you are using direct buffers, make sure you allocate the
appropriate amount of memory for the direct memory space. On Sun's JDK
that would be something like -XX:MaxDirectMemorySize=256m.

socket.appReadBufSize

(int)Each connection that is opened up in Tomcat get associated with
a read ByteBuffer. This attribute controls the size of this buffer. By
default this read buffer is sized at 8192 bytes. For lower
concurrency, you can increase this to buffer more data. For an extreme
amount of keep alive connections, decrease this number or increase your
heap size.

socket.appWriteBufSize

(int)Each connection that is opened up in Tomcat get associated with
a write ByteBuffer. This attribute controls the size of this buffer. By
default this write buffer is sized at 8192 bytes. For low
concurrency you can increase this to buffer more response data. For an
extreme amount of keep alive connections, decrease this number or
increase your heap size.
The default value here is pretty low, you should up it if you are not
dealing with tens of thousands concurrent connections.

socket.bufferPool

(int)The NIO connector uses a class called NioChannel that holds
elements linked to a socket. To reduce garbage collection, the NIO
connector caches these channel objects. This value specifies the size of
this cache. The default value is 500, and represents that
the cache will hold 500 NioChannel objects. Other values are
-1 for unlimited cache and 0 for no cache.

(int)Tomcat will cache SocketProcessor objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is 500. Other values are
-1 for unlimited cache and 0 for no cache.

socket.keyCache

(int)Tomcat will cache KeyAttachment objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is 500. Other values are
-1 for unlimited cache and 0 for no cache.

socket.eventCache

(int)Tomcat will cache PollerEvent objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is 500. Other values are
-1 for unlimited cache and 0 for no cache.

selectorPool.maxSelectors

(int)The max selectors to be used in the pool, to reduce selector
contention. Use this option when the command line
org.apache.tomcat.util.net.NioSelectorShared value is set
to false. Default value is 200.

selectorPool.maxSpareSelectors

(int)The max spare selectors to be used in the pool, to reduce
selector contention. When a selector is returned to the pool, the system
can decide to keep it or let it be GC'd. Use this option when the
command line org.apache.tomcat.util.net.NioSelectorShared
value is set to false. Default value is -1 (unlimited).

command-line-options

The following command line options are available for the NIO
connector:-Dorg.apache.tomcat.util.net.NioSelectorShared=true|false
- default is true. Set this value to false if you wish to
use a selector for each thread. When you set it to false, you can
control the size of the pool of selectors by using the
selectorPool.maxSelectors attribute.

NIO2 specific configuration

The following attributes are specific to the NIO2 connector.

Attribute

Description

useCaches

(bool)Use this attribute to enable or disable object caching to
reduce the amount of GC objects produced.
The default value is false.

socket.directBuffer

(bool)Boolean value, whether to use direct ByteBuffers or java mapped
ByteBuffers. Default is false.
When you are using direct buffers, make sure you allocate the
appropriate amount of memory for the direct memory space. On Sun's JDK
that would be something like -XX:MaxDirectMemorySize=256m.

socket.appReadBufSize

(int)Each connection that is opened up in Tomcat get associated with
a read ByteBuffer. This attribute controls the size of this buffer. By
default this read buffer is sized at 8192 bytes. For lower
concurrency, you can increase this to buffer more data. For an extreme
amount of keep alive connections, decrease this number or increase your
heap size.

socket.appWriteBufSize

(int)Each connection that is opened up in Tomcat get associated with
a write ByteBuffer. This attribute controls the size of this buffer. By
default this write buffer is sized at 8192 bytes. For low
concurrency you can increase this to buffer more response data. For an
extreme amount of keep alive connections, decrease this number or
increase your heap size.
The default value here is pretty low, you should up it if you are not
dealing with tens of thousands concurrent connections.

socket.bufferPoolSize

(int)The NIO2 connector uses a class called Nio2Channel that holds
elements linked to a socket. To reduce garbage collection, the NIO
connector caches these channel objects. This value specifies the size of
this cache. The default value is 500, and represents that
the cache will hold 500 Nio2Channel objects. Other values are
-1 for unlimited cache and 0 for no cache.

socket.processorCache

(int)Tomcat will cache SocketProcessor objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is 500. Other values are
-1 for unlimited cache and 0 for no cache.

socket.socketWrapperCache

(int)Tomcat will cache SocketWrapper objects to reduce garbage
collection. The integer value specifies how many objects to keep in the
cache at most. The default is 500. Other values are
-1 for unlimited cache and 0 for no cache.

APR/native specific configuration

The APR/native implementation supports the following attributes in
addition to the common Connector and AJP attributes listed above.

Attribute

Description

pollTime

Duration of a poll call in microseconds. Lowering this value will
slightly decrease latency of connections being kept alive in some cases
, but will use more CPU as more poll calls are being made. The default
value is 2000 (2ms).

pollerSize

Amount of sockets that the poller responsible for polling kept alive
connections can hold at a given time. Extra connections will be closed
right away. The default value is 8192, corresponding to 8192 keep-alive
connections.

Nested Components

None at this time.

Special Features

Proxy Support

The proxyName and proxyPort attributes can
be used when Tomcat is run behind a proxy server. These attributes
modify the values returned to web applications that call the
request.getServerName() and request.getServerPort()
methods, which are often used to construct absolute URLs for redirects.
Without configuring these attributes, the values returned would reflect
the server name and port on which the connection from the proxy server
was received, rather than the server name and port to whom the client
directed the original request.